1. Field of the Invention
The present invention relates to an optical inspection system and more particularly to a stereomicroscope with low eyestrain features and low operator interface requirements.
2. Description of the Related Art
Visual inspection tools are used in several industrial fields to inspect components and connections for defects which cannot be seen with the naked eye. Many industries have stringent magnification specifications which must be met in order for the inspected components and connections to meet desired specifications. In the soldering industry, especially the aerospace circuit board industry, solder connections must be inspected to meet desired specifications. Visual aids, such as stereomicroscopes, are used to increase the apparent size of the viewed solder connections. This increase in size enables an operator to better view and determine whether or not the solder connections meet desired specifications. Other applications will become apparent which utilize stereomicroscopes for inspection where viewing with the naked eye is inadequate.
The viewing of components through a visual inspection aid is enhanced by two-eye viewing. Two-eye viewing if correctly implemented enables the operator to reduce eyestrain; however prior stereomicroscopes have had very small, less than 0.1 inch diameter, exit pupils which require the operator to sit very still and carefully adjust the eyepiece separation in order to match his eye pupil separation (interpupillary distance) with that of the stereo-microscope. Such adjustments require expensive prism trains and mechanical fixturings to enable viewing of an object through the stereomicroscope. Small exit pupils also require the operator to remain nearly motionless while viewing through the stereomicroscope, which produces fatigue and eyestrain.
Although some stereomicroscopes have enlarged exit pupils, they do not allow freedom of motion of the operator's head and are susceptible to other operational problems. The MAC 2 stereomicroscope, manufactured by Projectina and imported from Switzerland by Soldering Technology International, Inc. of San Dimas, Calif., is an example of an existing stereomicroscope with relatively large exit pupils. Disadvantages of microscopes of this type include a small field of view; chromatic pupil aberrations; a large magnification difference between left and right eyepieces, which prohibits image fusion; interpupillary distance adjustments are required, and a head support is needed to keep the head from moving with respect to the pupils.
Known stereomicroscopes, in addition to not providing the operator with freedom of head motion, require the operator to view or "crane" the head and neck at awkward angles. In addition such microscopes fail to take advantage of natural eye tendencies such as known average interpupillary distances, the known average eye focusing distance, the known average eye toe-in, and the need for the eye to have a frame of reference. Thus, there is a need in the art for a stereomicroscope which overcomes the disadvantages of the above art stereoscopic inspection systems.